I have some experience on this field. Around two years ago i was a DevOp for the company running Dagbladet, Norways #2 newspaper. One of the things I did was keep an eye on mysterious traffic. I managed to find a huge spam network that set up a proxy service that delivered normal content, but injected "you can win an iPhone!" spam to all users visiting them. Since I was in the position of being able to monitor their…
As someone that tried reporting spam sites because they were using content scrapped from my website, I'm not surprised.
Cloudflare has a policy that they will not stop providing their IP hiding/reverse proxy services to anyone, regardless of complaints. The best they do is forward your complaint to the owner of the website, who is free to ignore it.
They say "we're not a hosting provider" as if that's an excuse that they can't refuse to offer their service. I'm sure many spam websites would go away if they couldn't hide behind Cloudflare.